Pipe end preparation tool having improved torque reacting and clamping capabilities

ABSTRACT

The present invention relates to a clamping device for clamping a mandrel to an elbow or pipe as well as to a torque-reacting device between a power unit housing and the mandrel. The torque reacting device has a pair of torque reacting keys mounted in a non-rotatable portion of the power unit housing, each of the keys having an end portion with converging opposite sides. The end portions of the torque reacting keys extend into correspondingly shaped, axially extending grooves formed in opposite sides of the mandrel. The opposite sides of the grooves are outwardly diverging and define an included angle approximately equal to the angle between the converging sides of the torque reacting keys. Adjusting screws are provided for each of the torque reacting keys. The clamping device has a plurality of clamping pins, each pin having a generally cylindrical shape with a hemispherical end portion defining a plurality of concentric ridges. An axially moveable actuating member bears on an a second end of the centering pins such that movement of the member along the longitudinal axis of the mandrel urges each of the centering pins into contact with the pipe surface.

This application is a division of application Ser. No. 373,517, filedJune 30, 1989.

BACKGROUND OF THE INVENTION

The present invention relates to a pipe end preparation tool havingimproved torque reacting and clamping capabilities in order to minimizethe time necessary to machine pipe ends.

Portable lathes for machining the ends of pipes are well known in theart and typically comprise a mandrel, a device to clamp the mandrel tothe pipe such that it is aligned with the center line of the pipe and apower unit mounted on the mandrel. The power unit has a rotatableportion, to which one or more machining tools are attached, and anon-rotatable portion slidably attached to the mandrel. Means areprovided on the power unit to move it axially along the mandrel in orderto feed the machining tools into the end of the pipe.

The power unit also comprises a drive mechanism, attachable to anexternal power source, to rotate the rotatable portion to which themachining tool is attached. Typically, a pneumatically or hydraulicallydriven motor is attached to the power unit such that its output shaft isdrivingly connected to the rotatable portion. The drive may includeinter-engaging bevel gears, one such bevel gear attached to an inputshaft, while the meshing bevel gear is affixed to the rotating portionof the power unit.

Clamping means are provided on one end of the mandrel to clamp it to thepipe. Such clamping means may be either external, to clamp the mandrelto the exterior of the pipe, or internal, wherein a portion of themandrel extends into and is clamped to the interior of the pipe. Theinternal clamping devices typically comprise a plurality of clampingmembers mounted on the mandrel so as to move in a radial direction withrespect to the longitudinal axis of the mandrel. The clamping membersare radially expanded or contracted by axial movement between wedgesurfaces formed on a portion of the mandrel and each of the clampingmembers. Such clamping members are usually formed as narrow, elongatedmembers having a significant length in the direction of the longitudinalaxis of the mandrel.

In order to minimize the time for machining the end of an elbow or apipe, it is necessary to take as large a cut per revolution of themachining tool as possible. The torque necessary to maximize the cutmust be reacted by the interconnection between the non-rotatable portionof the power unit and the mandrel, as well as through the deviceclamping the mandrel to the elbow or pipe. Torque reacting devices areknown which are designed to be interposed between the mandrel and thepower unit housing to increase their torque reacting capabilities.However, such devices are subject to shear forces and wear which requirethem to be replaced, since they are not adjustable to accommodate forsuch wear.

Elongated clamping members do not provide satisfactory results even whenthe mandrel is attached to an elongated pipe section in which there issufficient room within the interior of the pipe to accommodate thelength of the clamping members. The relatively narrow dimension of theknown clamping members does not provide the necessary clamping force toreact the torque generated during maximum cut machining operations.

Problems also arise when the mandrel must be attached to a pipe elbow orthe like, since there is usually not room within the interior toaccommodate the length of the elongated clamping members. Such knownclamping devices have failed to provide the necessary rigid support tothe mandrel to accurately machine the ends of the elbow.

SUMMARY OF THE INVENTION

The present invention relates to a clamping device for clamping amandrel to an elbow or pipe, as well as a torque-reacting deviceinterposed between the power unit housing and the mandrel in order toallow the cutting tool to take the maximum possible cut. The torquereacting device has a pair of torque reacting keys mounted in thenon-rotatable portion of the power unit housing, each of the keys havingan end portion with converging opposite sides. The end portions of thetorque reacting keys extend into correspondingly shaped, axiallyextending grooves formed in opposite sides of the mandrel. The oppositesides of the grooves are outwardly diverging and define an includedangle approximately equal to the angle between the converging sides ofthe torque reacting keys. Adjusting screws are provided for each of thetorque reacting keys and are located such that rotation of the screwsmove the torque reacting keys relative to the grooves in order toaccommodate for wear between the keys and the grooves.

A clamping device is provided on the end of the mandrel to clamp it to apipe. Where the portable lathe is to be attached to a pipe elbow or thelike, the clamping device has a plurality of clamping pins, each pinhaving a generally cylindrical shape with a hemispherical end portiondefining a plurality of concentric ridges. An axially moveable actuatingmember bears on a second end of the clamping pins such that movement ofthe member along the longitudinal axis of the mandrel urges each of theclamping pins into contact with the pipe surface. The ridges in contactwith the pipe elbow surface increase the clamping rigidity of themandrel, while at the same time minimizing the axial length of theclamping elements.

A clamping device having elongated clamping members may be used to clampthe mandrel to a straight length of pipe. The clamping members haveincreased width and bear on spaced apart grooves formed on the clampinghead to increase their torque reacting capabilities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view, partially in section, of a portable latheaccording to the invention;

FIG. 2 is a partial top view of the power unit shown in FIG. 1,partially broken away, illustrating the torque reacting key according tothe invention;

FIG. 3 is a side view of a mandrel according to the inventionillustrating a torque reacting groove;

FIG. 4 is an end view of the mandrel illustrated in FIG. 3;

FIG. 5 is a front view of a clamping pin according to the invention;

FIG. 6 is a cross sectional view taken along line B--B in FIG. 5;

FIG. 7 is an enlarged view of portion C of the clamping pin illustratedin FIG. 6;

FIG. 8 is a partial, exploded side view, partially broken away,illustrating an alternative embodiment of the clamping head according tothe invention;

FIG. 9 is a front view of the clamping head illustrated in FIG. 8.

FIG. 10 is a cross-sectional view of a torque reacting key according tothe invention;

FIG. 11 is an end view of the torque reacting key shown in FIG. 10;

FIG. 12 is a partial, cross-sectional view illustrating the engagementof a torque reacting key and a groove;

FIG. 13 is a side view of an alternative embodiment of the mandrelaccording to the invention;

FIG. 14 is a partial view of the mandrel of FIG. 13 with clampingmembers according to the invention;

FIG. 15 is a partial side view of the clamping end of the mandrel shownin FIG. 13;

FIG. 16 is a partial top view of the end of the mandrel shown in FIG.15;

FIG. 17 is an end view of the mandrel shown in FIG. 15;

FIG. 18 is a side view of the clamping member of FIG. 14;

FIG. 19 s a cross-sectional view taken along line D--D in FIG. 18.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The portable lathe according to the invention, as illustrated in FIG. 1,comprises a power unit 10 having a rotatable portion 12 and anon-rotatable portion 14. Rotatable portion 12 is rotatably supportedwithin portion 14 by bearings 16. One or more cutting tools (not shown)may be mounted on the face 12a in order to perform various machiningoperations on the end of a pipe elbow 18, or the like, as is well knownin the art. Although the invention will be described in terms of itsassociation with a pipe elbow, it is to be understood that the devicemay be equally applicable to machining the ends of straight lengths ofpipes and end flanges.

A power source (not shown) is attached to flange 20 such that the outputshaft of the power source drives input shaft 22 and bevel gear 24. Bevelgear 24 meshes with a corresponding bevel gear 26 fixedly attached tothe rotating portion 12.

The non-rotatable power unit housing portion 14 is slidably mounted onmandrel 28. The power unit 10 is moveable along the mandrel 28 indirections generally parallel to the longitudinal axis 30 of the mandrelby rotating feed ring 32 having handles 34 and being attached tothreaded feed member 36. Feed member 36 is threadingly engaged with feedthreads 39 formed on the exterior surface of a portion of the mandrel28. Thus, as is well known in the art, rotation of the handles 34 causesthe power unit 10 to move toward or away from the end of pipe elbow 18in order to bring the cutting tools (not shown) into, or move them outof contact with the pipe end. A handle 40 may be attached to thenon-rotating portion 14 to facilitate the manipulation of the tool, ifdesired.

The means for reacting the torque between the power unit portion 14 andthe mandrel 28 is best illustrated in FIGS. 2-4 and 10-12. FIG. 2 is aview showing one of the torque reacting keys 42 slidably mounted in abore defined by power unit portion 14 so as to be non-rotatably slidablein the directions indicated by arrows 44, a direction generallyperpendicular to the longitudinal axis 30 of mandrel 28. Torque reactingkey 42 may have a slot defined along one side which is engaged by aportion of set screw 46 to allow the key to move in the direction ofarrows 44, but prevent rotation thereof.

An end portion of the torque reacting key 42 extends into the openingextending through the power unit 10 to accommodate mandrel 28. The endportion has converging opposite sides 42a and 42b defining an includedangle α.

Adjusting screw 48 threadingly engages bore 50 defined by thenon-rotatable power unit portion 14 such that an end thereof bearsagainst one end of the torque reacting key 42. Adjusting screw 48defines an opening 52 therethrough to accommodate locking bolt 54 and todefine a polygonal opening portion 52a. As can be seen, the rotation ofadjusting screw 48 will exert a force on torque adjusting key 42 to moveit in the direction of arrows 44. Locking bolt 54, which passes throughadjusting screw 48 and is threadingly engaged with torque reaction key42 locks these elements in their adjusted positions by tightening thetorque reacting key 42 against adjusting screw 48.

An end portion of mandrel 28 defines generally longitudinally extendinggrooves 56 on diametrically opposite sides thereof. The grooves 56 haveoutwardly diverging sides 56a and 56b defining an included angle α,which is substantially equal to the included angle α defined between theconverging opposite sides 42a and 42b of the torque reacting key 42. Asseen in FIG. 12, the positions of the torque reacting keys 42 areadjusted so that the end portions enter grooves 56 such that surface 42acontacts surface 56a and surface 42b contacts surface 56b. The surfacesmay be in sliding contact with each other to permit the power unit 10 tomove axially along the mandrel 28, while at the same time, theinterengagement of the contact surfaces will react the torque imposedupon the power unit by the action of the cutting tool on the pipe end.

The angled contact surfaces 42a, 42b, 56a and 56b allow the position ofthe torque reacting key 42 to be adjusted relative to the mandrel 28 toaccommodate for any wear of these surfaces. By merely positioning thetorque reacting key further inwardly toward the mandrel axis 30, anywear of these surfaces may be taken up and the surfaces brought backinto contact with each other. This is not possible with the known torquereacting devices which utilize a rectangular cross sectional slot intowhich is inserted a correspondingly shaped torque reacting key. Once thegenerally parallel side surfaces of either the key or the groove becomeworn, it is impossible to adjust the key to compensate for the wornsurfaces. It is envisioned that the angle α will be approximately equalto 90°, although this value may vary depending upon the preciseapplication of the power unit and cutting tool.

The angled contact surfaces also reduce the shear forces imposed on thetorque reacting keys and the mandrel. The forces will extendperpendicular to the contact surfaces and, hence, only a portion thereofwill be directed at a right angle to the central axis of the torquereacting key to reduce the shear loads.

The other end of the mandrel 28 accommodates a clamping mechanism,generally indicated at 58. As best seen in FIG. 1, the clampingmechanism to clamp the mandrel to a pipe elbow 18 or the like comprisesa clamping head 60 having a plurality of clamping pins 62 slidably, butnon-rotatably, mounted therein. Although the clamping head isillustrated as having three such clamping pins, quite obviously othernumbers of pins may be utilized without exceeding the scope of thisinvention.

A typical clamping pin is shown in detail in FIGS. 5-7. The clamping pin62 has a generally cylindrical body portion with a generallyhemispherical first end portion 62a defining a plurality of concentricridges 64 thereon. The ridges 64 extend concentrically about the centralaxis of the general cylindrical body portion and form a clamping surfaceon the end of clamping pin 62 which has been discovered to markedlyincrease the clamping force of the device. Each of the concentric ridgeshas angled sides such that adjacent sides of adjacent ridges define anincluded angle β which may be between 50° and 70° and is preferably onthe order of 60°.

The clamping pin 62 also defines a generally longitudinally extendingslot 66 into which is inserted a portion of set screw 68 on the clampinghead 60 in order to prevent rotation of the clamping pin therein.Clamping pin 62 also defines an actuating surface 70 on a second end,which extends into the interior of the clamping head 60. Actuatingsurface 70 is a generally planar surface extending at an angle to thehorizontal and is adapted to be contacted by a correspondingly angledsurface 72a formed on actuating member 72. Actuating member 72 isslidably mounted in a central opening of mandrel 28 and is contacted bythreaded feed screw 74. Feed screw 74 extends through and is threadinglyengaged, with mandrel 28. Rotation of nut 76, which is fixed onto feedscrew 74, will cause rotation of feed screw 74, such rotation causingaxial movement of the feed screw 74 relative to the mandrel 28 due totheir threaded interconnection. Axial movement of feed screw 74 causesaxial movement of actuating member 72 which, in turn, causes generallyradial movement of the contact pins 62 through the interaction ofsurfaces 72a with surfaces 70. As seen in FIG. 1, as the clamping pins62 are urged outwardly, the ridges 64 will contact the interior of pipeelbow 18 thereby clamping the mandrel to the elbow.

The increased clamping force generated by the ridges 64 on the clampingpins 62 is of great importance in machining the ends of pipe elbows orother fittings wherein the curved nature of the fitting prevents anydeep clamping penetration by the mandrel. The curvature of theseelements prevents the use of elongated clamping members of the priorart. Attempts at shortening the axial length of the known clampingmembers has proven unsatisfactory insofar as they are then unable togenerate a clamping force sufficient to accommodate the weight andtorque imposed upon the mandrel by the power unit and the action of thecutting tool on the end of the fitting. The use of clamping pinsaccording to the invention not only enables the mandrel to be clamped tothe pipe elbow closely adjacent to the end thereof, but they provide arigid and stable mounting for the power unit to consequently increasethe accuracy of the machining.

An alternative embodiment of the mandrel and clamping head is shown inFIGS. 8 and 9 wherein the clamping head 60 is removably attached to themandrel 28. In this embodiment, the clamping head 60 is formed as aseparate element and is attached to flange 28a, formed on the mandrel28, by bolts 78 or the like. The clamping pins 62 and their actuationvia actuating member 72 are exactly the same as in the previouslydescribed embodiment. The use of different sized clamping heads allows acommon mandrel to be attached to various sizes of pipes. Also, differentlengths of the clamping pins may be accommodated by a given clampinghead to increase the range of pipe sizes to which the mandrel may beattached.

The invention also includes an improved clamping device for use onstraight pipe sections to increase the clamping force and rigidity ofthe mandrel attachment. As illustrated in FIGS. 13-19, mandrel 79defines grooves 56 on a portion thereof for interaction with the torquereacting keys of the power unit as in the previously describedembodiments. The clamping end of mandrel 79 defines a plurality ofbeveled surfaces 80, three of which are shown on the disclosedembodiment. However, it should be understood that different numbers ofbeveled surfaces may be utilized without exceeding the scope of thisinvention. Each beveled surface 80 has a pair of generally parallelclamping notches 82 formed thereon to slidably accommodate portions ofclamping members 84. A clamping member 84 is shown in detail in FIGS. 18and 19 and has a pair of laterally displaced bearing surfaces 84a spacedso as to slidably engage the notches 82. The width of the clampingmember 84 along with the lateral spacing of the surfaces 84a and thenotches 82 provide an increased clamping force to react the torquegenerated during the cutting operation. As seen in FIG. 14, the clampingmembers 84 are mounted on bevel surfaces 80 such that the surfaces 84aslidably contact notches 82. A spring 86 extending circumferentiallyaround mandrel 78 and through the clamping members 84 holds the clampingmembers on the mandrel 78 and urges them toward the center of themandrel.

The forward ends of the clamping members 84 engage actuating ring 88that is threadingly engaged with clamping screw 90. Clamping screw 90extends through a longitudinal opening in mandrel 78 and may be rotatedby nut 92 fixed on its opposite end. As can be seen, rotation of nut 92and feed screw 90 will cause actuating ring 88 to move axially withrespect to the mandrel 78, thereby urging the clamping members 84 alongbevel surfaces 80. This also causes the clamping members 84 to expandradially outwardly to engage the inner surface of the pipe into whichthe mandrel is inserted.

The foregoing description is provided for illustrative purposes only andshould not be construed as in any way limiting this invention, the scopeof which is defined solely by the appended claims.

What is claimed is:
 1. A clamping device for attaching a mandrel havinga longitudinal axis to pipe comprising:(a) a clamping head associatedwith the mandrel; (b) a plurality of clamping pins slidably mounted inthe clamping head so as to move in a direction substantiallyperpendicular to the longitudinal axis of the mandrel, each of theclamping pins having a central axis, a first end having a hemisphericalshape and a plurality of circular ridges extending concentrically aboutthe central axis on the first end of the clamping pin to form a clampingsurface which increases the clamping effect of the pins; and, (c) meansto move the clamping pins relative to the clamping head to urge theclamping surface on the first ends of the pins into contact with thepipes.
 2. The clamping device according to claim 1, wherein the means tomove the clamping pins comprises:(a) an actuating surface on a secondend of each of the clamping pins; and, (b) an actuating member mountedon the mandrel so as to move in a direction generally parallel to thelongitudinal axis of the mandrel and to contact the actuating surfacesof the clamping pins such that axial movement of the clamping pins. 3.The clamping device according to claim 1 further comprising attachingmeans to removably attach the clamping head to the mandrel.
 4. Aclamping pin for use in a device for clamping a mandrel to a pipecomprising:(a) a generally cylindrical body portion having first andsecond end portions, and a central axis, the first end portion having ahemispherical shape; (b) a plurality of circular ridges extendingconcentrically about the central axis on the first end portion to form aclamping surface; and, (c) an actuating surface defined by the secondend portion.
 5. The clamping pin according to claim 4 wherein each ridgehas sides such that the included angle between adjacent sides ofadjacent ridges is between 50° and 70°.
 6. The clamping pin according toclaim 5 wherein the included angle between adjacent sides of adjacentridges is approximately 60°.
 7. The clamping device according to claim 2wherein the clamping pin further comprises a generally cylindrical bodyportion between the first and second ends.
 8. The clamping deviceaccording to claim 1 wherein each ridge has sides such that the includedangle between adjacent sides of adjacent ridges is between 50° and 70°.9. The clamping device according to claim 8 wherein the included anglebetween adjacent sides of adjacent ridges is approximately 60°.